Internal-combustion engines have heretofore been convertible to burning gaseous fuel in addition to liquid fuel, generally by the replacement of the carburetor of the engine. That is, in addition to the normal addition of gaseous fuel tanks, selector valves, etc., most carburetors have been converted by adding a large and complicated auxiliary carburetor to the liquid fuel carburetor on the engine. In general, these auxiliary carburetors or conversion carburetors have occupied excessive space in the crowded engine compartment of the modern automobile and have been difficult to maintain. In some instances, the hood over the engine compartment had to be replaced or modified to accommodate the additional carburetion equipment. As a result, the full implementation of lower priced, pollution-reducing gaseous fuel has not been successful.